1. Field of the Invention
The present invention relates to tilt type steering devices, and is more particularly concerned with a tilt type steering device having an improved structure for supporting the steering column.
2. Related Background Art
There is already known a steering wheel height adjusting device or a so-called tilt type steering device wherein the height of the steering wheel can be changed according to physical characteristics, driving posture, etc. of the driver.
One such tilt type steering device is disclosed in U.S. Pat. No. 4,594,909.
The tilt type steering device described therein is of the so-called head-swinging type and is illustrated in FIGS. 14-17. A steering column 2 cylindrically formed to receive a steering shaft 1 is divided into two parts, namely, a lower steering column 3 and an upper steering column 4. The two steering columns 3 and 4 are connected at a supporting bracket 5 fixed on the vehicle body, such as at the bottom surface of a dashboard 8. The upper steering column 4 is pivotally supported from the supporting bracket 5 by a pair of pins 6,6, so as to be swingable about an axis defined by the pins (the tilt axis).
There is also provided a device which can be freely engaged or disengaged by the tilt lever 7 which swings around the tilt axis, so that the upper steering column 4 may be connected to the supporting bracket 5 (disabling the swinging of the upper steering column 4), or released from the supporting bracket 5 (enabling the swinging of the upper steering column 4).
A first gearing member 9 is fixed to the bottom of the upper steering column 4. A convex bottom surface of this first gearing member 9 is formed with first gear teeth 10 along a circular arc around the center of the tilt axis.
One end (left end in FIGS. 15 and 17) of a second gearing member 12 is pivotally supported from the supporting bracket 5 by a pin 11, so as to be pivotable on an axis defined by the pin 11. The upper edge of the other end (the upper edge at the right end of FIG. 15) of the second gearing member 12 is formed with second gear teeth 13. The second gearing member 12 pivots according to the swinging of tilt lever 7 to bring gear teeth 13 into and out of engagement with the first gear teeth 10.
A shaft 14 spanning the lower ends of the tilt lever 7 supports a roller 15, the upper portion thereof being in contact with the lower surface of the second gearing member 12.
A pin 18 projection from one side of the second gearing member 12 is engaged with an inclined long hole 17 formed in a swinging plate 16 fixed to the tilt lever 7.
In the foregoing construction, when the tilt lever 7 swings anticlockwise in FIG. 15, the roller 15 retreats from the lower part of the second gearing member 12 (the right end section in FIG. 15) and simultaneously, due to the engaging of the inclined long hole 17 and pin 18, the other end of the second gearing member 12 is displaced downward.
As a result, the second gear teeth 13 and the first gear teeth 10 are disengaged. The upper steering column 4 is thus free to swing about the tilting axis (within a restricted range of displacement allowed by a pin 19 projecting from a side of the upper steering column 4 into a circular arc-shaped long hole 20 formed in the supporting bracket 5) to adjust the height of steering wheel fixed to the end of the steering shaft 1.
When the height of the steering wheel is adjusted as aforesaid, the hand is taken off the tilt lever 7. Then the tilt lever 7 swings in clockwise direction in FIG. 15, due to pulling force of a tension spring 21, and roller 15 moves under the geared end the second gearing member 12, pushing such end of the second gearing member 12 upward to engage the second gear teeth 13 with the first gear teeth 10 so that the upper steering column 4 cannot turn around the tilt axis.
As a result, the steering wheel is held at the position set by adjustment of height. Under such state, an elastic force tending to cause clockwise swinging of tilt lever 7 in FIG. 15 is exerted on the tilt lever 7 by the tension spring 21 Therefore, the roller 15 cannot inadvertently retreat from the lower side of the second gearing member 12.
In the case of the conventional tilt type steering device which is constructed and used as aforesaid, the ends of the shaft 14 are suspended by a pair of suspension arms 22, 22, the upper ends of which are supported by the pins 6, 6. This increases the complexity of the device. Moreover, in order to secure sufficient strength of engagement of the first gear teeth 10 and the second gear teeth 13 and to secure sufficient rigidity for shaft 14, the components must be substantial. This increases the size of the device. The increased complexity and size naturally increase the cost of the device as well.
Another known head-swinging type tilt steering device is disclosed in Japanese Utility Model Appln. Laid-Open No. 62-4470. This device suffers from similar disadvantages to those above-discussed.